The wife, 2 teenagers (15 & 17 y.o.) and I are heading over to the UK for about 8 days in December and then travelling through Europe (France, Germany & Croatia) for about 3 weeks after that, all up trip is about 30 days. We intend to get 4 x Vodafone SIM only plans on arriving in the UK, and I’m finding all the offerings and alternatives a bit mind boggling. The PAYG plans seem to operate the same as what we call "Prepaid" here, though I was confused about something I read that said when your credit runs out you're charged at such and such a rate? Have I got that wrong?

Anyway, I'm after what you people in the know think would be the best SIM only plans for;

The Wife: Calls within UK and a few to other European countries organizing ahead, Texts back and forth to me and the kids, and then when we head to the other countries more local calls, texts and calls ahead etc. Also need a decent amount of data to web surf for information etc.

Me: Calls/Texts to the wife and kids – we’ll all be in the same city/area. Decent amount of data.

Kids: Texts/calls between family members whilst all in the same area. Lots of data.

They definitely need a credit limit so they can’t just rack up bills with excess data.

Big Value Bundle where for a set cost that is paid by topping up you get minutes, texts and data for 30 days. Any unused data rolls.over for another month.

Then there's the freebie tariff where you choose which allowance you want that afgain lasts 30 days and top up but with this you get to keep the top up credit to use when your allowances have been used up. They are similar to pre paid yes.

If a person say runs out of minutes from their tariff then any more.minutes would be charged for and comes out of any top up credit.

There are sim only contracts that last for 30 days or 12 months that come with allowances etc that again last 30 days. The newer tariffs have a data cap to stop someone going over their allowance and extra data can be added for a cost.

A person needs to pass a credit check and have a .uk address and bank account to have one of these.

Big Value Bundle where for a set cost that is paid by topping up you get minutes, texts and data for 30 days. Any unused data rolls.over for another month.

Then there's the freebie tariff where you choose which allowance you want that afgain lasts 30 days and top up but with this you get to keep the top up credit to use when your allowances have been used up. They are similar to pre paid yes.

If a person say runs out of minutes from their tariff then any more.minutes would be charged for and comes out of any top up credit.

There are sim only contracts that last for 30 days or 12 months that come with allowances etc that again last 30 days. The newer tariffs have a data cap to stop someone going over their allowance and extra data can be added for a cost.

A person needs to pass a credit check and have a .uk address and bank account to have one of these.

Something else to consider: if you are likely to want to call back to Australia from the UK, then it will be well worth opting into Vodafone International for any SIMs on which you might want to do so. It's free for PAYG (prepaid), and you can OPT IN by calling 36888 from the line in question.

As we only need it for 1 x 30 day period we have stop it renewing automatically by dialling a code?

She then opts in to Vodafone International and can call a landline in Australia for 5p a minute, or a mobile in Germany for 25p a minute. Are those call charges subtracted off the £20 amount until it goes down to zero and you run out of credit, or how does it work?

'If you don’t want your Big Value Bundle to automatically renew, you’ll need to opt out by calling 2345 free from your Vodafone mobile. You can end the automatic renewal at any time within your 30-day period.'

'If we can’t take your payment because you haven’t got enough credit, you’ll have 7 more days to top up (the ‘7-day period’). During this time, you will be charged our standard UK rates for minutes, texts and data until you top up. If, by the end of the 7th day, you still don’t have enough credit, you’ll be automatically opted out of the Big Value Bundle but you can opt back in at any time by buying another Big Value Bundle.'

As you'll be travelling in Europe for much of the time, you'll be able to use any inclusive minutes and texts within the countries, back to the UK and between yourselves. But I believe you'll be paying full cost for any calls to Aus, and possibly to other European countries - I haven't got time to check the latter, so perhaps someone else can advise.

The International Extra will only work for calls from the UK, not from other countries. "International" means "outbound"! So rather than buying that, simply opting in to Vodafone International and running with a £5 or £10 top-up may be more advantageous - depends on your likely pattern of usage.

Once you are travelling in Europe, you'll have a devil of a job trying to do any additional topping up, as you won't be able to use an Aus credit card online for topping up. So top up adequately before you move on, and possibly have an emergency top-up voucher to apply to whichever phone needs it.

If you don't have enough balance on the phone, the bundles won't renew, so you may not need to worry about opting out.

You won't be able to reclaim any balance left on the phones, so don't overstock! However, if you're going home from the UK, you will be able to donate any complete pounds to charity - I don't think the short code will work anywhere other than the UK. I've set up a number of possible options here, for precisely this sort of situation!